Fish ladder and its construction

ABSTRACT

The invention relates to a fish ladder (1) to by-pass a vertical descent (SH) in a flowing watercourse (31F) or a dam (31T), with an upstream water inlet (2) and a downstream water outlet (3) and with basins (4) arranged between them substantially in the downstream direction, each of which has an inflow slot (5Z) and an outflow slot (5A) as vertical through-flow slots (5) and deviating apparatus (6, 13) to form a meandering passage. The basins (4) have a partially cylindrical inner wall (40). Successive basins (4a, 4b, 4c, 4d) are arranged against one another and mutually laterally offset in such a way that the through-flow slots (5) run transversely to the direction of slope (G). The through-flow slots (5) are bounded on both sides by a first vertical partially cylindrical pipe (60) over the entire height (H) of the basin as a first diversion (6) with a substantially smaller radius in relation to that of the inner wall (40) of the basin.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a fishway to bypass a vertical descentin a flowing watercourse with an upstream water inlet and a downstreamwater outlet and with basins arranged between them substantially in adownstream direction, each of which has an inflow slot and an outflowslot as vertical through-flow slots and deflection means to form ameandering passage.

2. Prior Art

Fishways, particularly fish passes and fish ladders, enable migratingsalmonidae and small biocenoses to bypass dams, thereby restoring thepassableness of bodies of water.

From U.S. Pat. No. 132 349, a fishway according to the preamble isknown, which is made of substantially rectangular basins arranged on asloped ramp with deflection walls formed inside the basins. To create ameandering passage, the through-flow slots in the individual basins areprovided alternately in opposite deflection walls and in the cross wallsthat separate the individual basins. This design has the disadvantagethat the basin walls have sharp edges in the areas of the through-flowslots, which cause the steady flow to be disrupted at these locations,so that the fish who are migrating upstream become disoriented and getdiverted to the water surface by the turbulent flows and secondary flowsand potential change in the curvature path of the water flow in the areaof the through-flow slot. The fish are not oriented towards the bottomwhen they migrate upstream, and they depart from the flow rate of theflow profile that is ideal for their particular species.

Furthermore, dead spaces form in the comers of the basins, in whichdisadvantageous deposits of detritus accumulate that result incolmations and cause a considerable amount of maintenance work.

Since the ramp has an almost smooth surface, the dam in a flowingwatercourse represents an unsurmountable obstacle for small fish andbenthic organisms despite the fishway, because the flow rate near thebottom is too high.

In a technical essay ("Wasserwirtschaft 79 (1989) 2, page 67") afishway--the so-called vertical-slot pass--is described, which consistsof rectangular basins, which are arranged successively in the directionof the through-flow and whose cross walls have vertical through-flowslots. The through-flow slots are all formed adjacent to the samelongitudinal side of the system, which causes a highly irregular flowpattern (see FIG. 4b, page 68). Turbulent flows, which have adisorienting effect on the fish, are present both in the inlet area intothe basins and in the outlet area from the basins.

Because of their shape, the basins in the vertical-slot pass also havedead spaces where material is deposited, which can only be removed withcomplicated, time-consuming cleaning efforts.

To allow smaller fish to migrate upstream, the vertical-slot pass has abasin floor with a rough texture, which reduces the flow rate in thebottom area.

Practice has shown, however, that loose stones get stuck in thethrough-flow slots and block the passage, with the result that thecreatures are impeded in their migration upstream.

It is true that the vertical-slot pass is an improvement overconventional fishways such as rhomboid passes, or the like regarding thepassableness for migrating salmonidae and benthic organisms. However, itis not an ideal system under fluidics aspects since a basin shape withcomers not only furthers the formation of dead spaces but also thedevelopment of turbulent secondary flows, which are augmented further bysharp edges in the area of the through-flow slots.

Various fishways with round basins (the so-called round-basin passes)are furthermore known from a technical essay ("Wasser & Boden 47, (1995)3, p. 55 ff"), in which the round basins either have alternating pairsof cut-outs in the crest and base in the direction of the slope, orthrough-flow slots. These openings have sharp edges that result in theabove shortcomings, such as a detachment of the steady flow and theformation of turbulent flows. The flow does not run parallel to the baseof the basin but is directed upward so that the fish who are migratingupstream are receiving the message to swim towards the water surfaceinstead of remaining oriented towards the bottom.

The alternating orientation of the openings in the direction of theslope results in the formation of an undulating main flow in thesequentially traversed basins, whereby this main flow runs continuouslyin the direction of the slope and accordingly flows very fast, at timesexceeding the critical flow rates for small fish. To alleviate thisproblem, the slope is reduced to approximately 10% which, however,entails a disadvantageous increase in the number of required basins.

In the case of basins with a through-flow slot, the steel elementsmaking up the basin must be stabilized in the area of the through-flowslot with welded-in cross struts. This has the disadvantage that theflow is divided and disorienting vortexes are created.

Round-basin passes must therefore be assembled on-site, which is bothtime consuming and expensive.

Generally known are fishways whose rectangular basins have cut-outs inthe crest and holes for the creatures to slip through. Practice hasshown that many of these systems are not functional. The cause lies indesign errors and in the labor-intensive maintenance of these systems. Afurther shortcoming lies in the fact that systems of this type onlypermit the passage of certain species of fish, as the maximum velocitiesfor certain species of fish are exceeded at the slip-though holes. Smallcreatures cannot pass fish passes of this type. The basin passes withslip-through holes and crest cut-outs require a considerable amount ofmaintenance since the slip-through holes and crest cut-outs becomeclogged with flotsam, or the basins become filled with mud which, in theworst case, can make them impassable. The natural self-cleaning effectof these types of systems greatly depends on the flow rate and amount ofwater. The operability of this fishway is not guaranteed at low waterlevels as these systems require a great amount of water.

The problem of the passableness of flowing watercourses has also beenaddressed with an artificial creek, which is designed based on a naturalcreek and leads around the dam. This solution requires significantamounts of available space and water. Also, accompanying landscapingmeasures need to be carried out after the construction phase, resultingin considerable expenditures.

OBJECT OF THE SUMMARY OF THE INVENTION

The present invention furthermore relates to a fishway to bypass avertical descent created by a masonry dam of a catchment reservoir.

To make a catchment reservoir passable for fish, bypasses are knownwhich connect the reservoir area above the masonry dam with thedownstream region below the barrage dam, with the bypasses beinginstalled in the underground rock with a complex, expensive tunnelingtechnology. Since these bypasses follow the natural slope of the flowingwater that is to be dammed up, the distance to be covered is accordinglylong and renders these fish passes very expensive.

Based on the prior art, it is the object of the invention to improve afishway of the above type to present a compact, cost-effective, nearlymaintenance-free passage to allow migrating salmonidae and benthicorganisms, regardless of their species, to easily and safely bypass avertical descent created by a dam.

A second object of the invention consists of disclosing a fishway withwhich migrating salmonidae and benthic organisms can safely and easilybypass a very large vertical descent, for example in a catchmentreservoir, without resulting in great expenditures and complexinstallation.

It is furthermore a construction-related object of the invention toreveal a process for constructing partially cylindrical basins in afishway, which is characterized by low costs, a manufacturing processwith low labor content and nearly waste-free production.

This object is accomplished in accordance with the invention with thecharacteristics of claim 1. Additional advantageous designs of thefishway according to the invention are described in the sub-claims 2through 23.

To create a meandering passage, the fishway according to the inventionhas partially cylindrical basins arranged behind one another in thedirection of the slope, i.e., in the direction of the gradient, in sucha way that the successive basins are horizontally and vertically offsetfrom one another. Every second basin has the same orientation, so thatall openings of the basins are directed towards a center line extendingin the longitudinal direction of the fishway. As the water flows throughthe successive basins, the flow keeps altering its curvature path, withbasins of the same orientation having the same curvature path.

An individual basin consists of two opposite basin walls separated byvertical throughflow slots, with an upstream through-flow slot as aninflow slot into the basin and a downstream through-flow slot as anoutflow slot from the basin. The major portion of the inner basin wallis formed by a first basin wall made of a partially cylindrical piece ofpipe with a central angle of 180 to 350° and, accordingly, an openingsector with an opening angle of 180° to 10°. The opposite segmentforming a second basin wall is shorter than the diameter of the basinand is arranged within the opening sector, or the resulting hollowspace, of the first basin wall. At the same time this segment alsorepresents a connection piece for the adjoining edges of the basinsimmediately upstream and downstream with a different orientation.

The center points of the basins with the same orientation are located onan imaginary straight line extending in the direction of the slope. Thebasins preferably have base areas of identical sizes, so that the centerpoints of adjacent basins are located at the same distance from eachother. To construct a fishway along a sharp bend, the installed basinspreferably have different sizes and diameters.

The through-flow slots each run transversely to the direction of theslope. The position of the through-flow slots depends on the base areaof the basins; for example in semi-cylindrical basins, the through-flowslots may be located at a right angle to the slope or, in basins with anopening angle of less than 180°, the through-flow slots may be locatedat an oblique angle to the direction of slope. This advantageouslyresults in a meandering passage, which rises against the slope in aninlet or outlet area from the basins, from which inlet or outlet areathe flow passes along the inner wall of the basin, thus creating aself-cleaning effect in the basins. This has the advantage that thefishway according to the invention does not become filled with detritusand the required cleaning and maintenance efforts are relatively minor.Also, no dead spaces exist, which enhances the natural cleaning effectof the flow. Since no detritus is deposited in the basins and noturbulent flows occur, the fish do not become disoriented during theirmigration upstream.

The partially cylindrical shape of the basins and the arrangement of thethrough-flow slots furthermore have the result that the flow is directedtangentially into the respective basin. As a result, a laminar flow iscreated as an attraction flow for creatures who want to migrate upstreamso that they can easily and safely bypass the vertical descent.

Furthermore, the flow also does not get disrupted in the area of thethrough-flow slots and does not become detached from the inner walls ofthe basins, and all in all a low-turbulence flow pattern results.Accordingly, the design of the basins is physiologically optimallyadapted to the natural life-style of the fish as no confusing turbulentflows prevail in the fishway but the fish who wants to migrate upstreamis given unambiguous information in the form of the laminar flow.

Due to the design of the fishway according to the invention in the formof a meandering passage with partially cylindrical basins andthrough-flow slots oriented transversely to the direction of slope, theflow rate within a basin is reduced to almost zero from the basin wallto the center of the basin. This has the advantage that a resting zoneis formed in the vicinity of the basin center, where the fish and smallcreatures can linger during their migration. In this manner all benthicorganisms and migrating salmonidae can migrate upstream in the area ofthe flow that is ideal for them. Compared to the flow pattern in theknown systems, the meandering flow pattern in the fishway according tothe invention is characterized by a laminar profile.

The width of the through-flow slots is at least 30 mm, preferably atleast 45 mm, rendering the migration upstream in the vicinity of thebottom of the fishway safe for both small fish and large salmonidae, andindependent from the water levels in the basins. The through-flow slotsare furthermore bounded by a flow-directing deflection means along theentire height of the basins. A first flow-directing deflection means isa vertical, partially cylindrical pipe with a radius significantlysmaller than that of the inner basin walls.

Besides a decrease in the flow rate toward the center of the basin, theflow rate also decreases with an increasing height of the basins, thuspermitting the fish to migrate through the fishway at differentelevations.

In a preferred design of the fishway according to the invention, asecond, shorter partially cylindrical pipe is arranged over the firstpartially cylindrical pipe, resulting in a change of the cross sectionabove the height of the through-flow slot. The interior diameter of thissecond pipe is somewhat larger than the exterior diameter of the pipeimmediately underneath.

These pipes, which serve to round off the edges between successive basinwalls, are deflection means; two additional, partially cylindrical pipesof different lengths are preferably slipped over the first pipe asdeflection means, with the lowermost pipe having the largest diameterand the shortest length, so that the cross section of the through-flowslots decreases from the water surface to the bottom of the basin. Thecross section then has three steps, and as a result the rate of flow isnearly constant, except for an area near the bottom inside thethrough-flow slot, and the vertical flow pattern has several corridors.Inside the corridors the flow is augmented and a tunnel effect results,so that the fish migrate upstream in the area of the flow rate that isbest for them. The maximum flow rates for the fish species are notexceeded.

It is advantageous to provide a counter-berm in the outlet area from thebasins, particularly in basins whose bottom surface is larger than thearea of a semicircle. These counter berms preferably rise at the samevalue as the slope descends. This results in the formation of a flowinside the basins that runs parallel to the bottom of the basinregardless of its location. This has the advantage that bottom-dwellingfish are not misguided to the surface by a detachment of the flow fromthe bottom.

It is particularly advantageous if the basin floors have a rough textureto create a pattern of gaps that also allows benthic organisms tomigrate upstream while staying close to the bottom. In a preferreddesign, an amorphous, wide-meshed mat with interconnected hollow spacesis secured to the basin floor with the aid of cement. The use of a mathas advantages with respect to the construction process, and alsoeliminates the problem of clogged through-flow slots due to depositedstones, waste, driftwood, etc. This keeps the required amount ofmaintenance to a minimum, which, in turn, is reflected positively in lowoperating costs. Alternatively, sediments may be used to create thetexture of the basin floor.

A rough basin floor causes a reduction in the flow rate in the area nearthe bottom, so that small fish can migrate upstream as well. The gappattern with its hollow spaces, slits and crevices also allows smallcreatures to bypass the vertical descent created by the dam.

In a first embodiment, the basins have an area of a semicircle as theirbase and the pipe section has a center angle of 180°, and the oppositesegment forming the second basin wall is arranged on the diameter of thesemicircle. These segments are preferably slabs whose longitudinaldimensions are smaller than the diameter of the semi-cylindrical pipesection. The design of the fishway that is manufactured from thesesemi-cylindrical basins is particularly cost-effective and theindividual parts needed to construct the fishway come pre-assembled.

In a second embodiment, the basin has a base that is larger than thearea of a semicircle. The basin walls consist of a pipe section with acenter angle of preferably 300° so that the opening between the edges ofthis first basin wall has an opening angle of 60°. The opposite secondbasin wall is formed by another pipe section which is inserted with anexact fit between the adjacent edges of the basin walls immediatelyabove and below, and the second basin wall consequently represents aconnection piece between first basin walls with the same orientation.For the creation of a single basin, the second basin wall is preferablyarranged on a chord forming the circular arc of the first basin wall, sothat the area of the segment of a circle forming the base of the basinis larger than the area of a semicircle. The design of the fishway madewith these cylinder-section basins results in a fluidically idealmeandering passage. The flow is low in turbulence. This design of thebasins furthermore has the advantage that no waste is generated duringthe manufacture of the basins. Also, the individual pieces can bepreassembled for the construction of the fishway.

A third design is characterized by a very compact arrangement of thebasins. Like in the second embodiment, the individual components used toconstruct the fishway according to the invention consists of a firstpipe section with an opening angle of preferably 10 to 20° as a firstbasin wall, alternating with a second pipe section in the shape of apipe sector as the second basin wall. The two individual components ofthe system are arranged inside one another, offset from one another, sothat partial basins with nearly identical areas and elliptical crosssection are created within a basin, along with constrictions asthrough-flow slots between the deflection means and the opposite innerbasin walls.

To generate a meandering flow, a partially cylindrical pipe section isprovided behind the constrictions as a second deflection means. Thesebulges along the inner basin walls in the area of the inlet behind theconstriction into the lowermost of the three partial basins, have theeffect that the flow in this area is detached from the basin wall andflows into the next partial basin along a meandering pattern, withoutimpacting head-on into the wall of this basin.

This third embodiment of the fishway according to the invention isparticularly suitable for applications in catchment reservoirs where thelength of the available path is limited.

The fishway according to the invention is characterized by acomparatively small amount of required water as compared to conventionalfish ladders, and the flow conditions remain unvaryingly good evenduring major water level fluctuations in the upstream area of theflowing watercourse.

Fish must be guided into and through the fishways by attraction waters.An optimal attraction flow is attained by the acute angle of thedownstream outlet from the fishway into the flowing watercourse. Anattenuation of the attraction flow can be attained by means of a guidingand flow organ, which extends perpendicular to the water flow betweenthe river banks that bound the flowing watercourse on each side, andserves to guide run-off water from the dam to the downstream dischargetrench of the fishway.

The guiding and deflection means preferably consists of a larch-woodboard whose dimensions are adapted to the body of water and whichpreferably has a cross sectional area of 6×12 cm, which is installed atthe base of the dam. This guiding and deflection means at the base ofthe flood gate serves to additionally direct the residual water from thegates that let some water through into the lowermost basin of thefishway to augment the attraction flow at the entrance to this basin,and to prevent the formation of "secondary attraction flows".

In addition--depending on the individual situation--it may beadvantageous to have a fish guiding rake, which is guided transverselyto the run-off surface flow, e.g., behind a turbine system from riverbank to river bank, vertically down into the sediments.

The fishway according to the invention is connected, as one constructionunit, to the flowing watercourse via laterally secured connectiontrenches, with an upstream connection trench leading to the upstreamreservoir area above the dam and a downstream connection trench leadingto the downstream discharge area below the dam. The upstream connectiontrench preferably has a sturdy flap made of a fiber cement slab at itsinlet, which extends downward to the sediments of the reservoir area.The flap is open against the flow direction of the dammed up water. Thisdesign allows the returning eels to find the fish pass and they canmigrate unimpededly in the direction of the sea (Sargasso Sea spawninggrounds). This makes the invention particularly suitable as a so-calledeel slide.

The simple construction of the fishway furthermore makes itcost-effective. Particularly cost-effective is a construction withpre-assembled units, in which the basins are pre-mounted on apre-assembled steel scaffold, preferably hot galvanized, with glued-infloor slabs and cemented-in mats. A pre-assembled piece part is formedby several adjacent pipe sections of the same orientation with shortersections between them. The number of the basins that are pre-assembledon the prefabricated part depends on the total number of basins in thefishway, however, preferably three to four basins of the sameorientation are arranged successively to facilitate transportation andprovide for an easy final assembly on-site. This is another positiveaspect of the basins having the shape of a segment of a circle, as themodules can be inserted into one another for transportation purposes.

During the on-site assembly, depending on the individual requirements,either the preassembled version consisting of pre-manufacturedindividual components that are mounted on a steel ladder scaffold isinstalled with pre-fabricated separate concrete foundations along thecourse of the existing slope and connected to the reservoir area and thedownstream region as described, or the basins are mounted onto a slopedconcrete slab (ramp) that is constructed onsite and sealed with aspecial cement. All connecting points and gaps are grouted in withaluminous cement. Externally, the prefabricated parts are provided witha sloped cement grouting to protect them from shifting. An additionalseal can be provided if a special cement is used for this purpose. Thebasins are connected to one another with stainless-steel bolts andneoprene sealing disks. Slip-on deflection means forming thethrough-flow slots on the edges of the basin walls are pre-manufacturedfrom fiber cement pipes. They are secured to the basin ends of the basinwalls by means of stainless-steel screws and grouted in with aluminouscement mortar. The head ends are additionally rounded off

The slope or incline of the fishway is determined by the height offsetof the basins of maximally 25 cm, and by the individual basin diameters.The ability of the migrating species to climb or swim through thepartial meanders (first design) or full meanders (second and thirddesign) of the basins needs to be taken into consideration asappropriate.

To summarize in conclusion, the fishway according to the invention isvery well suited to meet the fluidics requirements for the prevention ofturbulences and for the formation of an attraction flow by means of alocal augmentation of the water volume in the discharge areas.

The system according to the invention is furthermore characterized by aparticularly simple construction and the option to construct bypre-assembled units.

The second object is accomplished according to the invention with thecharacteristics of patent claim 25, with the sub-claims 26 through 32presenting further advantageous designs of the fishway according to theinvention.

The fishway according to the invention for bypassing a vertical descentin a catchment reservoir created by a masonry dam consists of severalportions. One fishway, preferably the compact version with the third ofthe above basin shapes, is provided both in an upstream portion of thesystem on the reservoir side and in a downstream portion of the systemon the air space side. To form a meandering passage, the portions have aplurality of consecutive basins with partially cylindrical inner basinwalls, with constrictions as through-flow slots. Both portions areconnected via a connection channel that passes through the masonry dam.To enable the fish and benthic organisms to migrate through the fishwayregardless of the water level in the reservoir area, the basins in theupstream portion have an opening at the bottom. This opening can becontrolled via a slide, independently from the water level in thecatchment reservoir.

The slope in the fishway may be up to 30%.

In addition to the actual passage system, the fishway advantageouslycomprises an inverted-siphon system. The inverted-siphon system consistsof an upstream vertical siphon tube on the reservoir side and adownstream vertical siphon tube on the air space side, which areconnected by a siphon channel that extends horizontally through themasonry dam. The downstream siphon tube is connected to the downstreamportion of the fishway via at least one distribution channel. Bothsiphon tubes have openings that can be closed via slides to equalize thewater level. This design permits the equalization of the pressure orwater level between the catchment reservoir and a basin of thedownstream system portion which is arranged on the same height end ofthe upstream siphon tube.

The inverted-siphon system advantageously reduces the number of basinsin the upstream portion of the system. This fishway is a very compactshort-distance system.

Since no expensive earthwork, such as tunnel constructions, etc. isrequired to complete the fishway, this fishway, while providing at leastthe same effectiveness, is considerably less expensive than thetunneling method.

The construction-related object is achieved according to the inventionwith the characteristics of claim 33; the sub-claims 34 through 42present additional advantageous variations of the construction processaccording to the invention.

A pipe, specifically commercially available pipes of cement, glass-fibercement or other materials, is divided into a plurality of identical pipesections through cross cuts at a right angle to the pipe axisalternating with cuts at a cutting angle to the pipe axis that isdetermined by the slope of the fishway. From each of these pipe sectionsat least one pipe sector is cut out through coaxial cuts extendingparallel to the pipe axis, so that a partially cylindrical basin wall isobtained with an opening angle of 180 to 20°, depending on the basintype.

With basin types of semi-cylinders, the cut-out pipe sector is also asemi-cylinder, so that advantageously no waste is generated. If smallerpipe sectors with a center angle of less than 180° are manufactured, theleft-over pieces also are not discarded as waste, but instead used as asection forming a second, shorter basin wall in the direction of theslope, between consecutive adjacent basins of the same orientation. Itmay be necessary to reduce the size of the section with an additionalcoaxial cut parallel to the longitudinal axis.

With the process according to the invention the individual components ofthe fishway may be pre-assembled off-site, so that the on-siteinstallation can be performed quickly and easily. As a result, theinvestment costs will be low.

BRIEF DESCRIPTION OF THE DRAWINGS

The fishway is explained in more detail based on the FIGS. 1 through 15,with FIGS. 1 through 4 and 8 through 10 showing different preferredembodiments of the fishway. FIGS. 5 through 7 show a connection of thefishway to a flowing watercourse that is dammed by a weir, and FIGS. 11through 15 show a connection of the fishway to a catchment reservoir.The construction process according to the invention is explained indetail based on the sectional drawings in FIGS. 16 through 19. In thedrawings:

FIG. 1 shows a top view of a water outlet from a fishway withsemi-cylindrical basins (first embodiment),

FIG. 2 shows a longitudinal section through the fishway of FIG. 1,

FIG. 3 shows a top view of a fishway with nearly cylindrical basins withone opening (second embodiment),

FIG. 4 shows a longitudinal section through the fishway of FIG. 3,

FIG. 5 shows a schematic top view of a fishway according to FIG. 1integrated into a flowing watercourse as a bypass around a dam,

FIG. 6 shows a schematic top view of a fishway according to FIG. 3integrated into a flowing watercourse as a bypass around a bulkheadweir,

FIG. 7 shows a schematic top view of a fishway according to FIG. 3integrated into a flowing watercourse as a bypass around a side weir,

FIG. 8 shows a longitudinal section through a basin with counter-bermand a mat along the floor,

FIG. 9 shows a detailed top view of a connection of two walls ofsuccessive basins that are arranged in a longitudinal direction, and adeflection means encompassing the adjoining edges,

FIG. 10 shows a detailed top view of a portion of a fishway with threeelliptical partial basins (per basin) with nearly identical crosssections (third embodiment),

FIG. 11 shows a schematic top view of a fishway according to FIG. 3 withan upstream and a downstream portion, and a connection channel betweenthe two portions to bypass a vertical descent created by a masonry damin a catchment reservoir,

FIG. 12 shows a longitudinal section through the fishway according toFIG. 11,

FIG. 13 shows a schematic top view of a fishway according to FIG. 10with an upstream and a downstream portion and a connection channelbetween the two portions to bypass a vertical descent in a catchmentreservoir created by a masonry dam, and an inverted-siphon system,

FIG. 14 shows a longitudinal section through the fishway according toFIG. 13,

FIG. 15 shows a vertical view of the fishway according to FIG. 13,

FIG. 16 shows a sectional plan for a method of constructingsemi-cylindrical basins for a fishway,

FIG. 17 shows a top view of a semi-cylindrical basin,

FIG. 18 shows a sectional plan for a method of constructing nearlycylindrical basins with an opening for a fishway,

FIG. 19 shows a top view of basins with a segment of a circle as thebase area.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE INVENTION

The fishway (1) according to the invention with consecutive partiallycylindrical basins (4) arranged along an existing direction of slope (G)with through-flow slots (5) form a stair-like bypass around a dam (34)in a flowing watercourse (31F), for example a bulkhead weir, side weiror the like. The fishway (1) extends nearly parallel to the flowingwatercourse (31F) and is integrated as a compact construction unitalongside the dam (34), with an upstream connection trench (32) as anupstream water inlet (2) into the fish ladder (1) connecting thereservoir area (33) to the uppermost basin, and a downstream connectiontrench (35) as a downstream water outlet (3) from the fish ladder (1)connecting the lowermost basin to the downstream region.

Via the water inlet (2) the basins (4) are supplied with water from thereservoir area (33). After the water has passed through the basins (4)it exits the fishway (1) via the down-stream water outlet (3) into thedownstream region (36) of the flowing watercourse (31). After leavingthe flow (S) from the downstream connection trench (35) or the lowermostbasin, a laminar attraction flow with a very high flow rate forms whileentering the downstream region (36), which shows the fish who want tomigrate upstream the way into the fishway (1).

The diameter (d1) of the basins (4) depends on the local conditions,such as the vertical descent, length of the path or available space.However, financial and construction-related aspects, for exampleregarding the use of commercially available pipes, also factor into thedetermination of certain diameters (d1). The diameter (d1) of the basins(4) is between 0.8 to 5 m, preferably between 1 and 3 m; basins withlarger diameters (d1) are needed to attain very compact designs, whichare required for fishways that are integrated into catchment reservoirs(31T).--FIG. 10--.

The diameter (d1), which influences the flow rate, must be selected sothat the maximum flow velocities, which depend on the respective fishspecies, are not exceeded.

A height difference (height of fall) between successive basins (4, 4a,4b, 4c, 4d) is between 10 and 25 cm, preferably 15 cm, in the case ofsystems that are installed in flowing watercourses (31F), and 25 cm insystems (1) that are installed in catchment reservoirs (31T), since thisensures that the maximum flow rate of 1.10 m/sec is not exceeded in thebottom area. The selected height of fall depends on the species ofmigrating salmonidae that are present in the respective region.

The incline or slope (G) of the fishway (1) is determined by the heightdifference (height of fall) and the diameter (d1) of the basins (4). Theclimbing or swimming ability of the migrating creatures, such asmigrating salmonidae and benthic organisms, must be taken intoconsideration depending on the local conditions. A good compromisebetween the construction length of the fishway (1) and the maximum flowrate is attained at a relative slope (G) of around 20%; in individualcases the slope (G) is more gradual, however, not less than 14% orabove. In the case of very high vertical descents and limited availablespace, for example in catchment reservoirs (31T), the slope (G) may beup to 30%.

The height of the basins (4) depends on the shorter surface line of thesurface lines located in the plane of symmetry (SE) of the basin (4),which surface line has a length of at least 70 cm.

The fishway (1) according to the invention enables migrating salmonidaeand benthic organisms to bypass the vertical descent (SH) created by thedam (34) during their daily change of location or seasonal migration.

The fishway (1) comprises a plurality of basins (4) with identical basearea (4G), whose vertical through-flow slots (5) each form an inflowslot (5Z) and an outflow slot (5A).

Within the fishway (1), successive basins (4a, 4b, 4c, 4d) are orientedagainst one another to form a meandering passage, and offset laterallyso that the through-flow slots (5) run transversely to the direction ofslope (G). The flow (S) then changes its curvature path (SD) each timeas it flows through the successive basins (4) and passes tangentiallyalong the inner basin wall (40) in the inlet or outlet area (4EB, 4AB)of each basin. A meandering flow (S) forms, with sections that partiallyrise against the slope (G) in the outlet area (4AB) from the basin (4).

The basins (4) that have the same curvature path (SD) form two separatepiece parts (1E), which are separated by the through-flow slots (5) andrepresent the longitudinal sides of the fishway (1).

Each individual basin (4) consists of a plurality of basin walls (11,12), with a first basin wall (11) comprising of a randomly formedpartially cylindrical pipe section (41, 41*) and a second basin wall(12) located opposite the first basin wall (11) consisting of a segment(42, 42*), which connects adjacent edges (13a, 13b) of pipe sections(41, 41*) located immediately above and below. The two basin walls (11,12) are separated by an inflow slot (4Z) and an outflow slot (4A). Eachbasin (4) forms an element on one of the piece parts (1E) in the fishway(1), so that the piece parts (1E), depending on the number of basins (4)each comprise an alternating sequence of a pipe section (41, 41*) and aconnection piece (42, 42*). The basin walls (40) preferably comprisepre-constructed units of fiber cement or glass-fiber cement.

In the assembled condition, the adjoining edges (13a) of the basin walls(40) are encompassed vertically by a first partially cylindrical pipe(60) as a first deflection means (6) with significantly smaller radiusrelative to the radius of the inner basin walls (40), so that thethrough-flow slots (5) are bounded along the entire height of the basin.This prevents the flow (S) from being disrupted, especially in theoutlet area (4AB) of the basins (4), and the through-flow slots (5) arebounded in a manner which controls the flow. The width of thethrough-flow slots (5) is at least 30 mm, preferably at least 45 mm, sothat the fish do not get stuck in the through-flow slot (5).

The floor (28) of the basin has a rough texture to keep the flow ratelow in the area near the bottom and allow small fish and benthicorganisms to migrate upstream in the basins (4). To form a gap system,sediments (29S) of either fist size or child's head size are providedin/on the basin floor (28)--FIG. 2--or the basin floor (28) is coveredwith an amorphous, wide-meshed mat (29M) in the form of a fleece withinterconnected hollow spaces--FIG. 8--. The continuous transitionbetween the individual basins (4) enables all creatures to migratethrough the system.

FIGS. 1 and 2 show a first embodiment of the fishway (1) with basins (4)whose base areas (4G) are formed in the shape of a semicircle.

The pipe section (41) forming the first basin wall (11) has a centerangle (4ZW) of 180° and the connection piece (42T) forming the secondbasin wall (12) is a slab (42), whose length is shorter than thediameter (d1) of the semicircle or of the basin (4). To form a basin(4), the slab (42) is arranged on the diameter of the line forming thesemicircle, i.e., in the opening between the edges (13) of the firstbasin wall (12). The remaining distance to the adjacent inner basin wallforms the inflow slot and an outflow slot (5Z, 5A).

The center points of the diameter (dl) of the semicircle are located onan imaginary straight line (G1) extending in the direction of the slope(G), whereas the center points (MP) of the semi-cylindrical basins (4)are located on a zigzag line (V), so that all through-flow slots (5) areat a right angle to the slope (G) and an inlet and outlet flow (S),which pass tangentially along the inner basin wall, form in the area ofthe through-flow slots (5).

The fishway (1) comprises two piece parts (1E) consisting of successive,alternating half-pipe sections (41) and slabs (42*). For a finalassembly of the fishway (1), the piece parts (IE) that have beenprefabricated in the factory are transported to the construction site.Alternatively, the piece parts (1E) may also be assembled on-site in thedry. Afterwards the floor slabs (28P) are glued in and the prefabricatedbasin system is attached to a hot-galvanized steel ladder scaffoldingwhich is subsequently anchored in the river bank area with separateconcrete foundations (43).

This first embodiment is connected to the flowing watercourse (31F) viaa downstream connection trench (35) and an upstream connection trench(32) (not shown in the drawing). The connection trenches (32, 35) arefiber-cement channels with rectangular cross sections that are openalong the top, each of which connects the respective uppermost andlowermost semi-cylindrical basin (4) to the flowing watercourse (31F). Amulti-part construction permits an optimal flexible connection to theflowing watercourse (31F) and the construction principle also permitsthe construction of angular fishways (1).

FIG. 2 shows a through-flow slot (5) whose cross section changes alongits height. The constriction of the cross section reduces the amount ofwater required for a safe operation of the system (1) and permits aprecise adjustment of the water level. To change the cross section, twoshorter partially cylindrical pipes (61, 62) with an opening on theirlongitudinal sides are slipped on, as sleeves (61, 62) on both sides,over the deflection means (6), which bound the through-flow slot (5).These sleeves (61, 62) have a somewhat larger interior diameter--FIG.9--compared to the exterior diameter of the pipe (60, 61) locatedimmediately below.

Preferably, the through-flow slot (5) is narrowed on the floor side.Preferred graduations of the through-flow widths are 4.5 cm, 6.0 cm and8.5 cm at a water volume of 60 liters/sec or 8.0 cm, 10.5 and 13.0 cm ata water volume of 600 l/sec. For this purpose the edges (13) of thebasins (4) are encompassed by sleeves (60, 61, 62) with decreasinglengths and increasing diameters. Other graduations may, of course, bechosen depending on the requirements.

FIGS. 3 and 4 show the second embodiment of a fishway (1). The basins(4) consist of two pipe sections (41*, 42) of different sizes as a firstand second basin wall (11, 12), which are arranged opposite one anotherto form the segment of a circle as the base area (4G). The first basinwall (11) has a center angle of 300° and the second basin wall (12) hasa center angle of 50°. The second basin wall (12) is arrangedapproximately on the chord of the first basin wall (11).

The illustrated system (1) consists of eleven steps, with the firstbasin walls (11) oriented with their alternating openings (40) towardsthe center line (M) of the fishway (1). The center points (MP) of thebasins (4a, 4c; 4b, 4d) that have the same orientation are located ontwo parallel, imaginary straight lines (G1, G2) extending in thedirection of the slope (G). The center points (MP) of the successivebasins (4a, 4b, 4c, 4d) are located on an imaginary zigzag-shapedconnecting line (V) with the resulting angles between the sides allhaving the same size. The through-flow slots (5) are congruent with theconnecting line approximately in the center of a leg.

The basins (4) each form one step since the basin floor (28) does nothave an equal slope (G) within a basin (4), but is slanted in the inletarea (4EB) of the slope (G) and rises horizontally or slightly againstthe slope (G) in the outlet area (4AB) due to a counter-berm (8)--FIG.4--. The incline of the counter-berm (8) preferably has theapproximately same value as the slope (G). The successive basins (4a,4b, 4c, 4d) form a type of spiral staircase along an inclined plane witha walking line (flow line) broken by more than 1800 in each case, withthe head step (water inlet) (2) and entrance step (water outflow) (3)located on the same side of the staircase, i.e., on the side of thesteps facing the water.

The basins (4) furthermore have a flow-off channel (22) of fiber cement,for which the second basin wall (12) and the immediately adjacent firstbasin wall (11) of the subsequent basin (4) each have a semi-circularcut-out (18) at the upstream edge (16) of a common corner (17). Thevertex of the cut-out (18) is located approximately 15 cm from the upperedge of the basin (16). The center points of the cut-outs are located onan axis (21) so that a semi-circular shell (22) embedded into aluminousmortar can be inserted into the cut-outs (18). This flow-off channel(22) is flooded during high water and serves as an aid, especially forlarge salmonidae such as salmon and sea trout, to migrate upstream.

FIG. 4 shows the fishway (1) mounted onto a reinforced concrete slab(54). For its construction, a subbase (56) is excavated along theexisting slope (G) in the river bank area near the dam. On the outside,the basins (4) are secured onto the concrete slab (54) with galvanizedangles. Seams located on the interior between the basin floor (28) andthe basin walls (4) are sealed with a Thiocol joint or floor pavement.For stabilization, the basins (4) are supported on the exterior with aslanted cement footing (55) of a special cement, which at the same timealso has a sealing function. The basins (4) are interconnected withstainless steel bolts as shown in FIGS. 9 and 10. At least one partiallycylindrical pipe (60, 61, 62) is slipped over each edge (13) of thebasin walls (11, 12) as a sleeve (60, 61, 62), which is secured withstainless steel screws. The resulting hollow spaces are grouted in withaluminous cement and the head ends along the top are rounded.

After the assembly, the fishway (1) is integrated, as shown in FIG. 3,into the flowing watercourse (31F) via connection trenches (32, 35) tothe upstream reservoir area (33) and to the downstream region (36).These connection trenches (32, 35) are secured by palisades or concretewalls.

In FIGS. 5 through 7 the integration of a fishway (1) into a flowingwatercourse (31) with dam (34) is illustrated schematically.

In the embodiment of FIG. 5, a fishway (1) according to FIGS. 1 and 2 isintegrated parallel to a weir (34) in the corresponding river bank area(44), and additional sediments (29) are provided in the water outflow(3) to attenuate an attraction flow (S).

The trickling water (31) overflowing a weir (34) is collected via aguiding and deflection means (39) designed in the form of a channel, andpassed, via an adjoining discharge pipe (53), into the lowermost basin(4) of the system (1), thus augmenting the attraction flow at the outlet(3).

The water inflow (2) into the uppermost basin (4) has an adjustableinflow flap (37) or a slide arranged transversely to the flow (S), toregulate the amount of water entering. The flap (37) is preferablycontrolled in a manner so that the built-up pressure acting on theintake flap (37), which is generated by the flow traversing the dam(34), tightly closes this intake flap (37). Alternatively, a slide maybe provided. For maintenance work, the water inlet (2) into the fishway(1) is blocked off completely, so that the fishway (1) is drained.

FIG. 6 shows a bulkhead weir (34) in the flowing watercourse (31F) witha fishway (1) as a bypass according to FIGS. 3 and 4, with thedownstream connection trench (35) being arranged at an acute angle tothe downstream region (36) to reinforce the attraction flow. The wateroutflow (3) preferably discharges into the downstream region (36) at anangle of approximately 30° to the respective river bank.

The upstream and downstream connection trenches (32, 35) to the upstreamreservoir area (33) and the downstream outlet (36) of the flowingwatercourse (31F) are secured by palisades. In the inlet into theupstream connection trench (32), palisade bulkheads are provided to forma tapering funnel in the direction of the flow, and a threshold isprovided 30 cm below the water surface to catch any waste and preventflotsam from being carried into the system (1).

The trickle water (32) flowing off over the bulkhead weir (34) isdirected into the downstream connection trench (35) via a guiding anddeflection means (39) in the form of a plank of larch wood with a crosssection of 6×12 cm at the base of the gate support.

In FIG. 7, an analogous design of the fishway (1) of FIG. 6 is shown,with the flowing watercourse (31F) dammed by a side weir (34) and thedownstream connection trench (35) not arranged at an acute angle.

FIGS. 11 through 12 show a fishway (1) of glass-fiber cement accordingto FIGS. 3 and 4 that is integrated into a catchment reservoir (31T) tobypass a vertical descent (SH) created by a masonry dam (34M). In thiscase the vertical descent (SH) between a high water level (HHW) andtailwater level (UW) at the lowermost part of the base of the catchmentreservoir is approximately 40 m. The entire fishway (1) substantiallycomprises three portions (1U, 1O, 1V), namely an upstream system portion(1O) on the reservoir side, a downstream system portion (1U) on the airspace side and a connection channel (1V) connecting the two portions(1O, 1U) and passing through the masonry dam (34M).

The relationship between the vertical descent (SSH) on the reservoirside to the vertical descent (LSH) on the air space side ispredetermined by the maximum difference between the high water level(HHW) and the low-water level (NW) in the reservoir area (33). Here, themaximum difference between the high water level (HHW) and the low waterlevel (NW) is approximately 20 m, so each system portion (1U, 1O) mustbypass 20 m.

The basins (4) located in the upstream portion (10) of the system haveat least one opening on the bottom, which can be opened or closed bymeans of a slide, particularly by a hydraulically operated slide,depending on the headwater level in the catchment reservoir (33). Acombination with a float-actuated control is also advantageous. Thisensures that at least the lowermost basin (4) on the reservoir sidefunctions as an exit basin with a passage for the creatures inside thesystem, regardless of the headwater level (ZW) in the catchmentreservoir (33).

The upstream and the downstream portion (1O, 1U) of the system extendsalong the same river bank (3 8), with the number of basins (4) and thebasin type determining the slope (G) in the fishway (1)--the dashed linesymbolizes the steepest variation. The length (height) of the basins (4)of the upstream portion (1O) of the system continuously increases fromthe uppermost to the lowermost basin (4) by the predetermined height offall, with the lowermost basin (4) having a height from a parapet edgeof the masonry dam (34M) to the edge of the river bank at low waterlevel (NW). The basins (4) of the downstream portion (HU) of the systemhave the same height, a shorter surface line of the surface lines in theplane of symmetry of the basins (4) spans at least 70 cm.

To bypass a vertical descent (SH of 40 m, for example, 108 basins (4)are required in the upstream portion (1O) of the system at a fall heightof 18 cm (flat version) and 79 basins (4) at a fall height of 25 cm(steepest version); the number of basins (4) in the downstream portion(1U) of the system amounts to 126 for the flat version or 92 for thesteep version. The steep version saves a length of path of 25% in eachportion (1U, 1O), which can result in considerable savings in theinvestment and installation costs. Different versions may, of course, becombined.

The through-flow slots (5) in each portion (1U, 1O) of the system runtransversely to the existing slope (G), so that a meandering passage isformed.

FIGS. 13 through 15 show a further embodiment of a fishway (1)integrated into a catchment reservoir (31T) in the form of a structureresting against an existing structure. This third embodiment of thefishway (1) is characterized by a very compact design.

For space reasons, at least the upstream portion (1O) of the systemconsists of basins (4) with three inner partial basins (4T) as shown inFIG. 10, since only a short distance is available for the upstreamportion (1O) of the system. The slope (G) is approximately 30% here,with a height of fall of 25 cm. The upstream portion (1O) of the systemis supported on the floor side by angular supporting walls projectinginto the fluctuation area behind the masonry dam (34M).

The basins (4) according to FIG. 10 consist of two basin walls (11, 12),arranged in an opposite direction, made of pipe sections (41*, 42), witha first basin wall (11) having a center angle (4ZW) of approximately340° and a second basin wall (12) having a center angle (4ZW) ofapproximately 60°. In the following, the first basin wall (11) isreferred to as a long element and the second basin wall (12) as a shortelement, because of their different arc lengths.

The two piece parts (1E) forming the longitudinal sides of the fishway(1) comprise alternating successive short and long elements with thesame radius. The short elements (12) connect adjoining edges (13a, 13b)of the longer pipe sections (41*) of the same orientation locatedimmediately above and below. The center points (MP) of the long elementsof the same orientation each form an imaginary straight line (G1, G2)extending in the direction of the slope (G). To form three ellipticalpartial basins (4T) with nearly identical cross sections within onebasin (4), the two piece parts (1E) are arranged, interleaved andinterlocking with undercuts, in the direction of the slope (G) so thatthe imaginary straight lines (G1, G2) have a small parallel distancefrom each other.

Each basin (4) has several constrictions (5E) as through-flow slots(5)--FIG. 10--which constrictions (5E) are formed between the deflectionmeans (6) bounding the edges (13) of the inner basin walls (40) and theopposite inner basin wall (40). At an area (4AE) on the outflow side ofeach basin (4) a partially cylindrical pipe section (13) is provided asa second deflection means (63) on the inner basin wall (40) behind aconstriction (5E). These second deflection means (63) are installed at aright angle to the slope (G) so that a flow (S) that passes tangentiallyalong the inner basin wall (40) is generated in the through-flow slots(5).

In addition to the fishway (1) an inverted-siphon system (9) isintegrated into the catchment reservoir (31T), which consists of anupstream vertical siphon tube (9O) on the reservoir side, and adownstream vertical siphon tube (9U) on the air space side, and a siphonchannel (9V), which passes horizontally through the masonry dam (34M)and connects the two siphon tubes (9O, 9U). The downstream siphon tube(9U) is connected to the downstream portion of the fishway (1U) via adistribution channel (9K).

The inverted-siphon system (9) is required because the available pathlength in the upstream portion (1O) of the system is not sufficient tobypass the maximum difference between a high water level (HHW) and a lowwater level (NW) of approximately 20 m. With water levels (ZW) up to 12m below the high water level, the vertical descent (SH) can be bypassedwith the upstream portion (1O) of the system alone. Water levels belowthis intermediate water level (ZW) down to the low water level (NW),i.e., the remaining 8 m of the fluctuation range, are regulated via theinverted-siphon system (9). In the siphon tubes (9U, 9O), hydraulicallyoperated slides are provided to equalize the amount of water to thedownstream portion (1U) of the system.

Individual basins (4) of the downstream portion (1U) of the system areconnected with the downstream siphon tube (9U) via further distributionchannels (9K) so that fish counts can be performed for researchpurposes.

Additional resting basins (4R) with a significantly larger diameter (d2)relative to the diameter (d1) of the adjacent basins (4) are providedpreferably in the downstream portion (1U) of the system.

FIGS. 16 through 19 show sectional plans for the construction of basins(4) according to FIGS. 1 through 4 for a fishway (1).

First a pipe (45) is cut into pipe sections of equal size with a lengthof at least 70 cm via cuts crosswise to the pipe axis (45A). These cutsare cuts (QR) perpendicular to the pipe axis (45A), alternating withcuts (QS) at a cutting angle (α) to the pipe axis (45A), with thecutting angle (α) predetermined by a slope (G) in the fishway (1). Thecutting angle is between 10° and 40°, preferably between 15° and 20° forfishways (1) that are installed in flowing watercourses (31F), andbetween 20° and 30° for fishways (1) that are integrated into catchmentreservoirs (31T).

A sector piece (42) is subsequently cut from each of the individual pipesections (45T) with coaxial cuts (KS) parallel to the pipe axis (45A) onone side of the plane of symmetry (SE), in such a way that pipe sections(45T) with a partially cylindrical shape and opening are obtained. Theresulting pipe sections (41, 41 *) form a first basin wall (11) of apartially cylindrical basin (4).

The pipe (45) has a diameter (d1) of 0.8 to 5 m, preferably 1 to 3 m.Commercially available pipes (45) of fiber cement, glass-fiber cement orthe like are preferably used as the starting material.

With the process illustrated in FIGS. 16 and 17, basins (4) areconstructed with a semicircular base area (4G). For this purpose each ofthe individual pipe sections (45T) are divided into two equally sizedhalves (41) with coaxial cuts (KS) located in their plane of symmetry(SE), which halves can be integrated into the fishway (1) as first basinwalls (11) for the formation of a semi-cylindrical basin (4).

With the process illustrated in FIGS. 18 and 19, basins (4) with acircular segment as the base area (4G) are constructed in which theopening (4O) that results after the sector piece (42) has been cut out,has a center angle (ZW) between 10° and 180°, preferably between 20° and60°. The sector piece (42) is cut from the pipe section (45T) in thearea in which a bisecting plane of an angle (WE) of the formed sector(42, 4O) is perpendicular to the plane of symmetry (SE).

With further coaxial cuts the removed sector piece (42) is separatedinto at least two partial sections (42T) to produce connection pieces(42) forming second basin walls (12). These connection pieces (42) areused to close the gap between adjacent edges (13a, 13b) of adjacentbasins (4a, 4c, 4b, 4d) with the same orientation.

What is claimed is:
 1. A fishway to bypass a vertical descent with anupstream water inlet (2) and a downstream water outlet (3) and withbasins (4) arranged between them substantially in a downstream direction(G), each of which has an inflow slot (5Z) and an outflow slot (5A) asvertical through-flow slots (5), and deflection means (6) to form ameandering passage, characterized in that the basins (4) each have apartially cylindrical inner basin wall (40) and that the successivebasins (4a, 4b, 4c) are oriented against one another and offsetlaterally in such a way that the through-flow slots (5) run transverselyto the direction of slope (G) and that the through-flow slots (5) eachare bounded on both sides by a vertical partially cylindrical pipe (60)as a first deflection means (6) with a significantly smaller radiusalong the entire basin height relative to the radius of the inner basinwalls (40).
 2. A fishway according to claim 1, characterized in thatover the first partially cylindrical pipe (60) at least one second,shorter vertical partially cylindrical pipe (61, 62) is provided with asomewhat larger interior diameter compared to an exterior diameter ofthe pipe (60, 61) provided immediately underneath, so that a change incross section results above the height of the through-flow slot (5). 3.A fishway according to claim 1, characterized in that the width of thethrough-flow slot (5) is at least 30 mm, preferably at least 45 mm.
 4. Afish ladder according to claim 1, characterized in that the basins (4)have an identical base area (4G).
 5. A fish ladder according to claim 1,characterized in that successive basins (4, 4a, 4b, 4c) have a heightdifference (height of fall) from one basin to the other of approximately10 to 25 cm, preferably 15 cm.
 6. A fish ladder according to claim 1,characterized in that the shorter surface line of the surface lineslocated in the plane of symmetry (SE) of a basin (4) is at least 70 cm.7. A fish ladder according to claim 1, characterized in that the basinwalls (40) of an individual basin (4) are formed by a partiallycylindrical pipe section (41, 41*) as a first basin wall (11) and anopposite segment (42, 42*) as a second basin wall (12) and the segment(42) connects, as a connection piece, adjacent edges (13a, 13b) of thepipe sections immediately above and below belonging to the oppositebasins (4a, 4c) and these edges (13a, 13b) are encompassed by the firstdeflection means (6).
 8. A fishway according to claim 7, characterizedin that the pipe section (41*) has a center angle (4ZW) larger than180°, preferably 340°, and the segment (42, 42*) is arranged inside thepipe section (41*) in such a way that partial basins (4T) of nearlyidentical areas with an elliptic cross section are produced within abasin (4) and constrictions (5E) are produced as through-flow slots (5)between the deflection means (6) and the opposite inner basin walls (11,12).
 9. A fishway according to claim 8, characterized in that apartially cylindrical pipe section (13) is provided behind part of theconstrictions (5E) as a second deflection means (62).
 10. A fishwayaccording to claim 7, characterized in that the pipe section (41) has acenter angle (4ZW) of 180° and the segment (42, 42*) is arranged on thediameter of the semicircle.
 11. A fishway according to claim 7,characterized in that the second basin wall (12) is a pipe sector (42)with a shorter arc length relative to the arc length of the first basinwall (11) and that it curves in the opposite direction toward theopposite inner basin wall (40) to form an individual basin (4).
 12. Afishway according to claim 7, characterized in that the second basinwall (12) is a slab (42*) whose length is shorter than the diameter (d1)of the basins (4).
 13. A fishway according to claim 7, characterized inthat the basins (4) have a basin floor (28) with a rough texture to forma gap system (30) for which sediments (29S) of fist size to child's headsize and/or an amorphous wide-mesh mat (29M) with interconnected hollowspaces are provided along the floor of the basins (4).
 14. A fish ladderaccording to claim 1, characterized in that the pipe section (41, 41 *),as a circular arc, has a center angle (4ZW) larger than 180°, preferably300°, and that, to form a single basin (4), the segment (42, 42*) isarranged on a chord forming the circular arc, so that the area of thesegment of the circle forming the base (4G) of the basin (4) is largerthan the area of a semicircle.
 15. A fishway according to claim 14,characterized in that, to form a step in their outlet area (4AB) thebasins (4) have a counter-berm (8) with a basin floor (28), which ishorizontal or rises slightly against the slope (G).
 16. A fishwayaccording to claim 14, characterized in that the segment (42, 42*) andthe immediately adjoining pipe section (41*) each have a semi-circularcutout (18) on the upper edge (16) of a common comer, with the centerpoints of the areas of the semicircle being located in one axis (A) anda semi-circular shell (22) inserted into the cut-outs (18) as a flow-offchannel (22).
 17. A fishway according to claim 1, characterized in thatthe center points of the basins (4a, 4b; 4c, 4d) with the sameorientation each form an imaginary straight line (G1, G2) extending inthe direction of the slope.
 18. A fishway according to claim 17,characterized in that the center points are spaced at an equal distance.19. A fishway according to claim 1, characterized in that the fishway isa construction unit (1) forming a bypass around a dam (34) built to dama flowing watercourse (31F), and that it is connected to said flowingwatercourse (31F) by means of laterally secured connection trenches (32,35), with an upstream connection trench (32) leading out of thereservoir area (33) in front of the dam (34) and a downstream connectiontrench (35) leading into the downstream region (36) below the dam (34).20. A fishway according to claim 19, characterized in that theconnection trench (35) discharges into the downstream region (36) at anacute angle of preferrably 30° to the corresponding river bank.
 21. Afishway according to claim 19, characterized in that a guiding anddeflection means whose end facing the fishway is located in thedischarge area of the downstream connection trench (35) extendscrosswise in the downstream region between the lateral river banks (38).22. A fishway according to claim 1, characterized in that the fishway isa multi-part fishway (1) forming a bypass to bypass a masonry dam (34M)of a catchment basin (31T) in which an upstream portion (1O) of thesystem on the reservoir side of the masonry dam (34M) and a downstreamportion (1U) of the system on the air space side of the masonry dam(34M) are provided with a connection trench (35) to the downstreanregion (36), and both portions (1O, 1U) are connected via a connectionchannel (1V) that passes through the masonry dam (34M).
 23. A fishwayaccording to claim 1, characterized in that the fishway comprisespre-assembled piece parts (1E) with pipe sections (41, 41*) of the thefishway orientation and connection pieces (42, 42*) between them, whichcan be anchored with separate foundations (43) on a floor slab (28P) inthe area of the river bank (44).
 24. A process to construct a basinfor/in a fishway, particularly according to claim 1, comprising thesteps of:separating a pipe into a plurality of pipe sections (45T) ofthe same size by means of cross cuts (QR) perpendicular to the pipe axis(45A) alternating with cross cuts (QS) at a cutting angle (W) to thepipe axis (45A), with the cutting angle (W) determined by the slope (G)in the fishway (1), and subsequently using the individual pipe sections(45T) to construct at least one partially cylindrical basin wall (40) bymeans of coaxial cuts (KS) parallel to the pipe axis (45A).
 25. Aprocess according to claim 24, characterized in that the cutting angle(w) α lies between from 10 and 40°, preferably from 15° and 20° forflowing watercourses (31F) and between 20° and 30° for fishways (1) thatare integrated into catchment reservoirs (31T).
 26. A process accordingto claim 24, characterized in that the pipe sections (45T) have a lengthof at least 70 cm.
 27. A process according to claim 24, furthercomprising the step of:cutting a sector piece (42) from the individualpipe sections (45T) to form a basin wall (40) with an opening (4O) bymeans of coaxial cuts (KS) arranged on one side of its plane or symmetry(SE).
 28. A process according to claim 27, characterized in that thesector piece (42) is cut from the pipe section (45T) in the area inwhich a plane (WE) bisecting the angle of the opening (40) isperpendicular to the plane of symmetry (SE).
 29. A process according toclaim 27, characterized in that the sector piece (42) has a center angle(4ZW) between 10 and 180°, preferably between 20 and 60°.
 30. A processaccording to claim 24, comprising the steps of:dividing the individualpipe sections (45T) into two halves (41) of equal size by means ofcoaxial cuts (KS1) along their planes of symmetry (SE) and integratingthese halves into the fishway (1) as basin walls (40) to form asemi-cylindrical basin (41).
 31. A process according to claim 24,further comprising the steps of:dividing the sector piece (42) by meansof at least one further coaxial cut (KS2) into at least two segments(42T) and integrating the two segments into the fishway (1) betweenadjacent edges (13a, 13b) of adjacent basin walls (4a, 4c) with the sameorientation to form a basin (4).
 32. A process according to claim 24,characterized in that the pipe (45) has a diameter (d1) of 0.8 to 5 m,preferably 1 to 3 m.
 33. A process according to claim 24, characterizedin that the pipes (45) are made of fiber cement or glass-fiber cement.34. The fishway to bypass a vertical descent in a catchment reservoircreated by a masonry dam, with an upstream portion (1O) of the system onthe reservoir side and a downstream portion (1U) of the system on theair space side, and between them a connection channel (1V) passingthrough the masonry dam (61), in which the portions (1U, 1O) comprise aplurality of successive basins (4) with partially cylindrical innerbasin walls (40) to form a meandering passage and furthermore compriseconstrictions (SE) as through-flow slots (5), and the basins (4) locatedin the upstream portion (1O) of the system have at least one opening onthe floor side, whose passableness for the creatures who are migratingupstream can be regulated by a slide depending on the amount of waterpresent in the catchment reservoir,wherein the successive basins (4a,4b, 4c, 4d) have alternating orientations and are laterally offset fromeach other so that the through-flow slots (5) in each portion (1U, 10)of the system run transversely to the existing slope (G) and that thethrough-flow slots (5) are bounded along the entire basin height by avertical partially cylindrical pipe (60) as a first deflection means (6)with a significantly smaller radius relative the radius of the innerbasin walls (40).
 35. A fishway according to claim 34, characterized inthat one single basin (4) is formed by two basin walls (11, 12) that areoriented against one another, of which a first basin wall (11) has acenter angle (4ZW) of approximately 340° and a second basin wall (12)has a center angle (4ZW) of approximately 60°, and the second basin wall(12) is a connection piece (42, 42*) to connect adjoining edges (13a,13b) of the basin walls (40) immediately above and below belonging tothe opposite basins (4a, 4c; 4b, 4d).
 36. A fishway according to claim34, characterized in that the center points of the basins (4) with thesame orientation each form an imaginary straight line (G1, G2) extendingin the direction of the slope (G) and the straight lines (G1, G2) have asmall parallel distance from one another, so that three partial basinsare created within one basin (4).
 37. A fishway according to one orseveral of the claims 34 to 36, characterized in that the fishway has aslope (G) of approximately 30°.
 38. A fishway according to claim 34,characterized in that the basins (4) in the upstream portion (1O) extendfrom one parapet edge of the masonry dam (34M) maximally to the bottomof the catchment reservoir and the height of the basin (4) in thedownstream portion (1U) amounts to at least 70 cm.
 39. A fishwayaccording to claim 25, characterized in thatin addition to the fishway(1) an inverted-siphon system (9) is integrated into the catchmentreservoir (31 T), which comprises an upstream vertical siphon tube (9O)on the reservoir side and a downstream vertical siphon tube (9U) on theair space side and a siphon channel (9V), which passes horizontallythrough the masonry dam (34M) and connects the two siphon tubes (9O,9U), and that the downstream siphon tube (9U) is connected to thedownstream portion (1U) of the fishway (1) via at least one distributionchannel (9K), and that both siphon tubes (1U, 1O) have openings that canbe closed by means of a slide to balance the water level in thedownstream portion (1U) of the system.
 40. A fishway according to claim39, characterized in that several basins (4) of the downstream portion(IU) are connected to the downstream siphon tube (9U) by means ofadditional distribution channels.
 41. A fishway according to claim 34,characterized in that at least one resting basin (4R) with asignificantly larger diameter (d2) relative to the diameter (d1) of theadjacent basins (4) is integrated into the downstream portion (1U) ofthe fishway (1).